This invention relates generally to medical implants. More particularly, this invention relates to implantable prostheses that resist capsular contracture. The implant in its preferred form is a mammary prosthesis which is well known in the art. Other applications include adjustable mammary prostheses and mammary tissue expanders. Most specifically, this invention relates to a preferred method of assembling the implantable prosthesis that allows a surgeon to efficiently and accurately do so immediately prior to insertion into the human body.
The use of implantable breast prostheses has become an acceptable and popular practice to enhance the aesthetic breast form whether for augmentation, reconstruction, or revision needs. These devices generally comprise a nonreactive, flexible outer surface or shell which contains a gel or liquid filler.
Undesirably, when inserted into the host, the implant is recognized as a foreign body by the host's immune system and is walled off, or encapsulated, from the rest of the host's body. Encapsulation can result in many unwanted effects. To combat encapsulation, surgical correction is often required. Despite documented high patient satisfaction rates and enhancement of quality of life, surgical correction or re-operation rates can be unacceptably high. In fact, recently published FDA PMA (pre- and post-market approval) studies on the silicone gel breast implants document the severity of the public need. Within four years of the initial operation, over twenty-three percent of all primary augmentation patients had to undergo a re-operation. Approximately forty percent of these re-operations were to correct capsular contracture. Thirty-five percent of these revision patients had to undergo another operation, and the leading cause was again capsular contracture. Patients undergoing primary breast reconstruction with silicone gel breast implants (following mastectomy for cancer) have an even greater public need for help. Twenty-three-point-five percent of these women must undergo a re-operation, and the leading cause was capsular contracture or implant malposition (usually due to capsular contracture). Thirty-three percent of these revision patients need another revision. The re-operation rates for women with saline implants are similar, and again, capsular contracture is the leading culprit.
The inability to control abhorrent scarring or encapsulation process leads to spherical capsular contracture (often accompanied by implant displacement, distortion and pain and discomfort). Spherical capsular contracture is the number one cause of the aforementioned excessive re-operation rates. Other causes of re-operation include implant displacement and palpability of the implant through the skin.
Spherical capsular contracture has remained a particularly vexing problem for scientists, surgeons, and patients for almost 50 years. Although silicone elastomers (often comprising the outer surface of the implant) are considered inert materials, the host nonetheless reacts to their in-vivo implantation by treating the implant as a “foreign body” by walling the implant off from the surrounding host tissue by the formation of a fibrous sheath surrounding the implant's peripheral surface. This naturally occurring process is harmless, unless the degree of linear scar formation becomes excessive, and the capsule tightens or contracts around the implanted silicone device, causing shape distortion, implant displacement, implant palpability, and patient pain and discomfort. These specific adverse affects are the leading cause of the FDA's documented excessive re-operation rates. Breast implant patients endure these adverse affects due to the inability to control device-host tissue reaction.
Intra-operative tissue manipulations, which have been advocated as possible remedies to the capsule contracture problem, include the creation of large surgical pockets in which the implant is placed, atraumatic surgical technique, use of sub-muscular surgical pockets for implant placement, and pocket irrigation with steroid and/or antibiotic containing liquid. Post surgical exercises or implant displacement manipulations have been advised, as have arm movements and body position maneuvers. (See Maxwell, G P; Hartley, R W; “Breast Augmentation”, Mathers: Plastic Surgery, Second Edition. (Ed) Saunders Philadelphia, Vol 6. p 1, 2006).
Improvements and alterations to the design of breast implants have also been initiated in an effort to reduce spherical capsular contracture and visibility and palpation. For example, U.S. Pat. No. 4,889,744 advocates that texturization of the outer surface of the implant will minimize capsule contracture around an implant. U.S. Pat. No. 4,648,880 utilizes an outer polymeric covering of a woven mesh draped over the implant to reduce scar formation. Further, U.S. Pat. No. 6,913,626, submits that capsule contracture can be reduced by covering the elastomeric shell of the implant with a bio-absorbable covering.
For unrelated uses in the human body, biologically-derived materials have been developed from allograft and xenograft (such as porcine or bovine) source and treated in a way (biotechnologically prepared) to serve as dermal graft tissue matrixes. These biologically-derived materials (generally acellular dermis in composition) are thought to serve as a non-absorbable collagen scaffold, to promote the organization of the healing process, thereby promoting re-generative repair rather than scar formation. These materials have been used primarily to correct large wounds, hernias, and other defects caused by trauma or surgical extirpation for cancer. Examples of this type of biological material, specifically allograft or xenograft acellular dermal grafts or matrixes, include (but are not limited to) Alloderm and Strattice from Life Cell Corporation, Cosmatrix/Surgimend from TEI Biosciences, Neoform from Tutogen Medical, and Dermamatrix from MTF. It has not, however, been anticipated in any of these applications that the materials become an interfaced component of a medical implant.
The main functional use of these acellular dermal materials in the prior art has been as a tissue extension or tissue replacement (tissue supplement) of the abdominal musculature and/or facial defects in repairing abdominal wall hernias, ventral hernia repair. In these situations the abdominal musculature is stretched, weakened, or rendered inadequate for repair, and, thus, the need for the supplemental tissue substitute.
Another use of these materials has been as a tissue extension, supplement, or replacement following cancer extirpation of the breast. Here the pectoralis major muscle is partially removed, stretched, or inadequate to provide tissue coverage of the underlying reconstruction. Thus the dermal graft is used “to simulate total muscle coverage using tissue like materials over the lower lateral aspect” of the underlying reconstruction (“an alloderm sling”). (See Gamboa-Bobadilla, G. M.; Implant Breast Reconstruction using Acellular Dermal Matrix, Annals of Plastic Surgery, 56; p. 22, 2006; Salzberg, C. A.; Nonexpansive immediate breast reconstruction using human acellular tissue matrix graft, Annals of Plastic Surgery, 57, p. 1, 2006). In these various applications, the acellular dermal graft “serves the function of native tissue.” (Spear, S.; Use of Regenerative Human Acellular Tissue to Reconstruct the Abdominal Wall following Pedicle TRAM Flap Breast Reconstruction; Plastic Reconstructive Surgery 118, p. 8, 2006. Spear, S. L., Pelletiere, C. V., and Lockwood, M. Immediate Breast Reconstruction with Tissue Expanders and Alloderm, Plastic Reconstructive Surgery of the Breast, p. 489, 2006).
In addition, prior art acellular dermal grafts have been used for soft tissue deficient patients with “pectoral muscle denervation.” (See Duncan, D. I. Correction of Implant rippling using allograft dermis. Aesthetic Surgery Journal 21, p. 81, 2001). In these applications, the native tissue was inadequate because of “very thin skin flaps.” Id. In this prior use the graft was also secured “into the vascularized recipient site” of the host tissue to serve as an extension of the pectoral muscle. Id. The purpose was “soft tissue augmentation” to cover externally visible “rippling” of an underlying device (“rippling” can only be seen or present when capsule contracture is not present around a breast implant). Id. Another way to describe this prior art is that the dermal graft is used as a replacement, extension, or supplement of the native tissue, regardless of that which it covers.
Although the prior art has proffered myriad solutions to reduce spherical capsular contracture associated with implantable prostheses, all have proved to be less than optimal. Thus, what is needed is an implant having an integral interfaced component comprised of an acellular dermal graft material (the effectiveness of the interfaced implant being neither dependent on the texture of the implant's surface nor the dissolution of a covering) to reduce capsular contracture, implant displacement, and/or implant palpability.